“This message contains blocked content that has previously been flagged as abusive or spammy. Let us know if you think this is an error.”

We should note that j.mp is a service from Bit.ly, a respected, well-funded player in the URL shortening space.

A possible explanation is that there were an unusual amount of rogue j.mp URLs linking to malicious websites or spam sites, triggering Facebook’s automatic blocking mechanism. We’ve contacted Facebook to see if that’s indeed the case, or if there’s something else at play here, but we’ve not immediately received a response.

For what it’s worth, Bit.ly says it uses data from a number of independent sources (including Sophos, Websense, VeriSign, PhishTank, and Google Safe Browsing) in addition to proprietary internal classifiers to determine whether or not destination sites of shortened URLs propogate spam, viruses, or other malware.

Aside from that, the company also boasts that they have a “huge stream of people and companies” flagging offending sites or sites that appear as spam.

You can still post bit.ly links to Facebook, and customized shortened URLs like our own tcrn.ch (which is powered by Bit.ly) also don’t seem to pose any problems.

For more insight on the relationship between Bit.ly and Facebook (which also has a custom link shortener with FB.me) see here and here.

We’ll update when we learn more about the issue, and if and when it will be resolved.